The ability to sense and respond to mechanical force and changes in cell volume is a universal property of all cells. Mechanical signaling via mechanosensitive ion channels plays a key role in many cellular and organismal processes. Cell volume regulation is an essential housekeeping function and is mediated in part by ion channels that sense cell size. With few exceptions, the genes that encode these channels have eluded molecular identification. C. elegans offers unique experimental advantage for defining the physiological roles and regulation of ion channels. However, a major disadvantage is the relative inaccessibility of its cells for detailed electrophysiological characterization. To circumvent this limitation, the investigator's group developed techniques to routinely isolate and patch clamp C. elegans embryo cells and oocytes. They discovered a novel, abundantly expressed outwardly rectifying mechanosensitive anion current, ICl, mec, and a robust inwardly rectifying swelling-activated anion current, IClir, swell. The proposed studies will characterize the functional properties and regulation of the ICl, mec and IClir, swell channels, and will test the hypothesis that they are encoded by one or more of the 6 C. elegans ClC anion channel genes. The embryonic and oocyte expression patterns of the 20 identified DEG/EnaC cation channel genes will be also characterized as these channels play key roles in C. elegans mechanosensory behavior. Knowledge of expression patterns will allow the investigator to study channel function by patch clamp in native cells and to determine whether DEG/ENaCs are mechanically gated. The combination of genomic analysis, cellular and molecular biology methods, and electrophysiological measurement of channel activity will be used.